1. Field of the Invention
The present invention relates to electronic circuits for the replication of musical tones and in particular relates to a programmable circuit for generating and manipulating sequences of complex tones.
2. Description of the Prior Art
Circuits for the synthesis of music have typically involved complex electromechanical combinations for the reproduction of musical sounds such as is disclosed in U.S. Pat. No. 2,940,351. In electronic musical instruments or sound synthesizers the musical tones are produced by a plurality of analog oscillators and analog wave-shaping circuits, or if implemented with digital circuitry, produce tones selectively read from a read-only memory coupled to a speaker through a digital-to-analog converter. Such circuits fail to incorporate any playback mechanism wherein after a series of tones have been entered they may be selectively played back or further manipulated. In other words, prior digital circuitry for electronic musical instruments or synthesizers generally incorporates a nonprogrammable, real time output.
A typical sound synthesizer, utilizing digital circuitry, such as in a speech synthesizer, involve circuits which use a control circuit to selectively draw fixed sound patterns from a memory for direct coupling through a digital-to-analog converter for audio reproduction as is disclosed in U.S. Pat. No. 3,641,496; 3,928,722; or 3,892,919. Words or sounds are thus synthesized by drawing from a fixed library of basic prestored sound elements and selectively combining the sound elements by fixed circuitry to obtain a digitized composite of the final sound. No provision is provided to programmably alter or manipulate the stored sounds.
Thus, musical compositions are generally composed in the mind of the composer, recorded on paper and manually played on an instrument capable of fixed tone characteristics, such as a piano. The true sound of the composition as produced by a live orchestra cannot be determined until actually played by the actual orchestra. The actual sound of the composition is predicted by the composer based only upon experience. Any reiterations of the composition can only be rendered through actual rehearsal performances. What is needed is an apparatus which can arbitrarily simulate a musical tone or sound and which will allow the composer to selectively alter the quality and characteristics of each tone in a reiterative process to obtain the desired orchestrated sound.